Prior Art Discussion
The use of organic binders for ceramic powders is a well established commercial practice. U.S. Pat. No. Re. 28,195 reissued Oct. 8, 1974, on U.S. Pat. No. 3,755,204 to Frank J. Sergeys and commonly assigned with the present application discloses a method of preparing porous-ceramic exhaust oxidation catalysts from ceramic powder filled, plasticized polyolefins. The disclosed method involves homogeneously blending a composition containing a polyolefin, a ceramic filler and a plasticizer; shaping the composition into an appropriate form; extracting the plasticizer with a solvent, and firing the extracted form to remove the polyolefin.
In actual practice it has been found that when fired under normal ceramic firing conditions the above-mentioned structures invariably develop cracks. To date the solution to this problem has been to fire the structures under carefully controlled reducing conditions up to the temperature where the organic binder has been removed, presumably by evaporation. This method is wasteful of fuel, because excess gas is used to secure the reducing kiln atmosphere. It is also difficult because continuous monitoring of the kiln atmosphere is required to insure net reducing conditions.